1. Field of the Invention
This invention relates to solar cell module array and method for installing solar cell modules.
2. Related Background Art
Recently, solar power generation has been attracting much attention because of its cleanness, viewed from resources- and energy-saving considerations, and is gradually going into the domestic area. At present, the solar cell modules are installed on existing facilities, such as house roofs and building walls, and newly built facilities represented by frames on the ground and building roofs. These modules are installed on, e.g.,:
(1) frames, and
(2) roofs, in which they are assembled to form monolithic structures.
Generally, a plurality of solar cells are electrically connected to each other, to form a solar cell module array.
The solar cell modules are combined with each other for practical use, and generally shaped in such a way that they are compatible with each other. Therefore, they are rectangular or virtually triangular (virtually right triangular) in the case of (1), and shaped to be easily adaptable to rectangular roofs in the case of (2).
The modules falling into the category (1) are mounted on a frame, built to securely hold them. The modules commercialized at present are shaped rectangular or square, or virtually triangular. They are installed by a method in which a plurality of the same type of rectangular modules are combined with each other to form an array, or another method in which one type of rectangular module(s) and another type of triangular module(s) are combined with each other. The latter method is suitably used on a hip roof: when rectangular modules are installed on a hip roof, because there are dead spaces, right triangular in each row, formed in the vicinity of the corners, and it is possible to install more modules and increase output by installing triangular modules in the dead spaces.
FIG. 1 illustrates the conventional arrangement in which rectangular modules are combined with triangular modules, where 201 is a plane on which the modules are set, 202 is a rectangular module and 203 is a triangular module.
On the other hand, the modules falling into the category (2), where they are assembled in a roof to form a monolithic structure, are shaped generally similar to the roof. Needing no frame, they are assembled more easily and cause no damage of the beauty. They are mostly rectangular, and a plurality of modules of the same type are assembled to form an array.
FIG. 2 illustrates the conventional arrangement in which only rectangular modules are used, where 204 is a plane on which the modules are set, and 205 is a rectangular module.
As described above, it is common to assemble solar cell modules of the same size into an array, when modules of the same type are to be used.
However, there are many roof types, e.g., hip, gale, square and irimoya (gable type in the upper, with 4 roof planes in the lower). Therefore, it is difficult for the conventional module installation method to efficiently arrange them. The problems are described concretely, below:
FIGS. 3A and 3B show rectangular solar cells arranged on a trapezoidal plane, seen in a hip roof or the like, by the conventional method in which modules of the same type are assembled, where 1401 is a plane on which the modules are set, 1403 is a rectangular module and 1402 is a dead space. Generally, solar cells cannot be cut freely on the site, and a dead space is formed on the plane, irrespective of modular width, as shown in the figure (gray portion).
Therefore, triangular modules have been used to minimize the dead space, which however, involves some problems, for example, when the triangular module and plane on which the modules are set are slanted at significantly different angles. This is illustrated in FIG. 4, where 1501 is a plane on which the modules are set, 1503 and 1504 are rectangular and triangular modules, respectively, and 1502 is a dead space. As shown, it is difficult for the conventional method to arrange triangular modules efficiently. The dead space could be greatly reduced, when triangle modules of varying angle are arranged on each plane. This, however, should increase module production cost, both for triangular modules and matching rectangular modules.
FIGS. 5A and 5B illustrate solar cell modules each consisting of a plurality of rectangular cells, where 1601 is a rectangular module and 1603 is a rectangular cell in FIG. 5A, and 1602 is a triangular module and 1603 is a rectangular cell (the same one as that in FIG. 5A) in FIG. 5B.
For modules assembled in a roof, the upper and lower joints must deviate from each other (tongue-and-groove joint) for weathering considerations, and triangular modules cannot be efficiently arranged in this case. This type of module is generally narrow, increasing module production and installation costs, when a triangular module is used, because of decreased unit module area and increased area on which narrow modules are installed.
The dead space could be reduced to use the installation plane more efficiently by decreasing size of each rectangular module, which, however, should greatly increase the installation cost, because of increased number of cells to be electrically connected to each other and of increased difficulty of installation.
This also causes another module installation problem, i.e., significantly limited array design resulting from narrowed range of inverter input voltage.
For example, consider the following procedural steps for array design and module installation:
1) Determination of solar cell modules and inverters to be used
2) Calculation of maximum number of solar cells which can be installed on a plane
3) Determination of number of cells for each string from a range of inverter input voltage
4) Determination of number of modules to be connected in series, from the number of cells determined in the step 3)
5) Determination of maximum numbers of cells to be connected in series and parallel, which satisfy the cell number limitation determined in the step 2)
In this case, number of modules to be connected in series is limited from the range of inverter input voltage, when only modules of the same type are used. As a result, number of cells may be limited to below the allowable level for the installation plane or string.
It is an object of the present invention to provide methods for installing solar cell module arrays and solar cell modules, which reduce a dead space and allow more efficient utilization of the plane on which the modules are set by solving the above problems.
It is an object of the present invention to provide a solar cell module array comprising two or more different types of modules, wherein said two or more different types of modules are rectangular, having different lengths from each other.
It is another object of the present invention to provide a roof provided with a solar cell system comprised of two or more different types of solar cell modules installed on a given plane, wherein said two or more different types of modules are rectangular, having different lengths from each other.
It is further object of the present invention to provide a method for installing two or more different types of solar cell modules on a given plane, wherein said two or more different types of modules are rectangular, having different lengths from each other.